A heterogeneous cell surface glycoprotein termed 170K glycoprotein is detectable by cell surface or metabolic labeling on various normal fibroblast cell lines. The 170K glycoprotein is absent or decreased in transformed cells, and exhibits a cell-cell contact dependent accumulation on the surface of normal fibroblasts. The heterogeneity of 170K is due to the presence of at least two physically similar glycoproteins termed procollagen and GP170. GP170 is antigenically related to the major cell surface, transformation sensitive glycoprotein, Gap a (fibronectin). One component of the 170K glycoprotein complex interacts with intermediate filaments, and may play a role in communication of information from the cell surface to the cytoplasm via the cytoskeleton. The following research application proposes to investigate: (1)\the similarities and differences between GP170 and Gap a in terms of carbohydrate and protein content, (2)\possible mechanisms for the interconversion of GP170 and Gap a, (3)\which component of 170K interacts with intermediate filaments and the control for the interaction, (4)\the basis for the cell surface accumulation of 170K glycoprotein and other membrane glycoproteins as a result of cell contact.